The present invention relates to a scrub washing apparatus and scrub washing method for washing a substrate such as a semiconductor wafer and an LCD glass substrate.
In manufacturing steps of semiconductor devises, a single-processing substrate washing system is used for removing contaminants, such as particles, organic compounds, and metal ions, attached to a surface of a semiconductor wafer. The single-processing substrate washing system has a scrub washing apparatus for scrubbing away attached materials (contaminants) from the surface of the wafer by brining a brush or a sponge (hereinafter referred to as "scrub member") into contact with the wafer in rotation.
The scrub washing apparatus has a swingable horizontal arm, a vertical output shaft arranged at a tip portion of the horizontal arm, a scrub member directly or indirectly supported by the vertical output shaft, a rotation drive means for driving the rotation of the scrub member together with the vertical output shaft, and a press means for pressing the scrub member downward together with the vertical output shaft. A contact pressure of the scrub member to the substrate (hereinafter referred to as "scrub contact pressure") corresponds to a total force of a press force given to the scrub member by the press means and a weight of the scrub member itself. The surface of the substrate is desirably washed by properly controlling conditions including the scrub contact pressure, a rotation speed of the scrub member, a moving speed of the scrub member, and a rotation speed of the substrate, in accordance with the surface state of the substrate.
Such a scrub apparatus is disclosed in Japanese Patent Application KOKAI publication Nos. 8-141518, 8-141519. In these conventional apparatuses, an expandable bellows mechanism and an air cylinder mechanism are employed as the press means. For example, in the bellows mechanism described in Japanese Patent Application KOKAI 8-141518, the press force is applied to the vertical output shaft by expanding and contracting of the bellows fitted at an upper end of the vertical output shaft. In the air cylinder mechanism, the press force is applied from the cylinder to the vertical output shaft by protruding or retracting a piston rod attached to an upper end of the vertical output shaft. However, in the conventional apparatuses, if a rub resistance between the vertical output shaft and a bearing is changed, the press force may not be desirably transmitted to the scrub member. Since a belt mechanism is used as a rotation drive mean in the conventional apparatus, the rotation force may not be desirably transmitted to the scrub member because the tension of the belt varies. Furthermore, a driving force transmission mechanism of the conventional apparatus is complicated in structure since numerous mechanical elements such as a belt, a pulley, a bellows, an air cylinder, and a bearing, are assembled, resulting in generation of particles in a non-negligible amount. The generated particles are attached to the substrate, degrading the cleanliness of the substrate surface.